Cavity blackbody radiation source and method of making the same

ABSTRACT

A cavity black body radiation source is provided. The cavity black body radiation source comprises a blackbody radiation cavity, a black lacquer, and a carbon nanotube layer. The blackbody radiation cavity comprises an inner surface. The black lacquer is located on the inner surface. The carbon nanotube layer is located on a surface of the black lacquer away from the blackbody radiation cavity. The carbon nanotube layer comprises a plurality of carbon nanotubes and a plurality of microporous. A method of making the cavity blackbody radiation source is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201810027802.X, filed on Jan. 11, 2018, inthe China Intellectual Property Office, the contents of which are herebyincorporated by reference. The application is also related to copendingapplications entitled, “CAVITY BLACKBODY RADIATION SOURCE AND METHOD OFMAKING THE SAME”, filed ______ (Atty. Docket No. US72200). Theapplication is also related to copending applications entitled, “CAVITYBLACKBODY RADIATION SOURCE”, filed ______ (Atty. Docket No. US72201).The application is also related to copending applications entitled,“PLANE SOURCE BLACKBODY”, filed ______ (Atty. Docket No. US72202). Theapplication is also related to copending applications entitled, “CAVITYBLACKBODY RADIATION SOURCE AND METHOD OF MAKING THE SAME”, filed ______(Atty. Docket No. US72203). The application is also related to copendingapplications entitled, “PLANE SOURCE BLACKBODY”, filed ______ (Atty.Docket No. US72205). The application is also related to copendingapplications entitled, “ ”, filed ______ Docket No. US72189). Theapplication is also related to copending applications entitled, “ ”,filed ______ (Atty. Docket No. US72195). The application is also relatedto copending applications entitled, “ ”, filed ______ (Atty. Docket No.US72196). The application is also related to copending applicationsentitled, “ ”, filed ______ (Atty. Docket No. US72197). The applicationis also related to copending applications entitled, “ ”, filed ______(Atty. Docket No. US72198). The application is also related to copendingapplications entitled, “ ”, filed ______ (Atty. Docket No. US72199).

FIELD

The present disclosure relates to a cavity blackbody radiation sourceand a method for making the same.

BACKGROUND

With a rapid development of infrared remote sensing technology, theinfrared remote sensing technology is widely used in military andcivilian fields, such as earth exploration, weather forecasting, andenvironmental monitoring. However, all infrared detectors need to becalibrated by a blackbody before they can be used. The higher anemissivity of the blackbody, the higher an accuracy of a calibration ofthe infrared detector. An effective emissivity of a cavity blackbodymainly depends on an opening size of the cavity blackbody, a shape ofthe cavity blackbody, an emissivity of a material inside the cavityblackbody, and an isothermal degree in the cavity blackbody. Therefore,selecting high emissivity intracavity surface materials has a greatsignificance for obtaining high performance blackbody radiation sources.

DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a section structure diagram of one embodiment of a cavityblackbody radiation source.

FIG. 2 is a scanning electron microscope (SEM) image of a drawn carbonnanotube film.

FIG. 3 is an SEM image of a pressed carbon nanotube film comprising aplurality of carbon nanotubes arranges along a same direction.

FIG. 4 is an SEM image of a pressed carbon nanotube film comprising aplurality of carbon nanotubes arranges along different directions.

FIG. 5 is an SEM image of a flocculated carbon nanotube film.

FIG. 6 is a flow diagram of a method of making the cavity blackbodyradiation source in FIG. 1.

FIG. 7 is a section structure diagram of one embodiment of a cavityblackbody radiation source.

FIG. 8 is a flow diagram of a method of making the cavity blackbodyradiation source in FIG. 7.

DETAILED DESCRIPTION

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “another,” “an,” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean “at leastone.”

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale, and the proportions of certain parts havebeen exaggerated to better illustrate details and features of thepresent disclosure.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape, or other feature which is described, suchthat the component need not be exactly or strictly conforming to such afeature. The term “comprise,” when utilized, means “include, but notnecessarily limited to”; it specifically indicates open-ended inclusionor membership in the so-described combination, group, series, and thelike.

FIG. 1 shows a cavity blackbody radiation source 10 of one embodiment.The cavity black body radiation source 10 comprises a blackbodyradiation cavity 11 and a carbon nanotube layer 12. The blackbodyradiation cavity 11 comprises an inner surface. The carbon nanotubelayer 12 is located on the inner surface. The carbon nanotube layer 12comprises at least one carbon nanotube film.

The blackbody radiation cavity 11 is made of a material resistant tohigh temperature and having a high emissivity. The blackbody radiationcavity 11 can be made of hard aluminum material, aluminum alloy materialor oxygen-free copper. The blackbody radiation cavity 11 comprises ablackbody cavity 110 and a blackbody cavity bottom 111. The blackbodycavity 110 and the blackbody cavity bottom 111 can be an integralstructure. The blackbody cavity 110 and the blackbody cavity bottom 111can also be two independent structures, and the blackbody cavity bottom111 can be pressed into or can be screwed into the blackbody cavity 110from an end opening of the blackbody cavity 110.

The blackbody cavity 110 comprises a room 112. A cross section of theroom 112 can be circle, ellipse, triangle, quad, or other polygon. Ashape of a bottom surface of the room 112 is not limited. The shape ofthe bottom surface of the room 112 can be a flat surface, a taperedsurface, a prismatic surface, or other surfaces.

The cavity blackbody radiation source 10 can further comprise a heatingelement. In one embodiment, the heating element comprises a carbonnanotube structure, a first electrode and a second electrode, the firstelectrode and the second electrode are located on a surface of thecarbon nanotube structure and spaced apart from each other. The carbonnanotube structure is wrapped or wound around an outer surface of theblackbody radiation cavity 11. The carbon nanotube structure comprisesat least one carbon nanotube film or at least one carbon nanotube wire.The carbon nanotube structure comprises a plurality of carbon nanotubesconnected end to end and arranged in a preferred orientation. Theplurality of carbon nanotubes of the carbon nanotube structure extendsfrom the first electrode to the second electrode.

Because the carbon nanotube structure is wrapped or wound around theouter surface of the blackbody radiation cavity 11, after the carbonnanotube structure is energized by the first electrode and the secondelectrode, the carbon nanotube structure can heat the whole blackbodyradiation cavity 11. So that a temperature field inside the blackbodyradiation cavity 11 is evenly distributed, the temperature stability anduniformity of the cavity blackbody radiation source 10 can be improved.Since carbon nanotube has small density and light weight, using thecarbon nanotube structure as the heating element allows the cavityblackbody radiation source 10 to have a lighter weight. Since carbonnanotubes have high electrothermal conversion efficiency and low thermalresistance, and the carbon nanotube structure has small resistance;using the carbon nanotube structure to heat the blackbody radiationcavity has the characteristics of rapid temperature rise, small thermalhysteresis and fast heat exchange rate. Carbon nanotubes have goodtoughness, and thus the cavity blackbody radiation sources using thecarbon nanotube structure as heating element have a long service life.

The at least one carbon nanotube film of the carbon nanotube layer 12can be a drawn carbon nanotube film, a flocculated carbon nanotube filmor a pressed carbon nanotube film. When the carbon nanotube layer 12comprises only one carbon nanotube film, the carbon nanotube layer 12comprises one drawn carbon nanotube film, one flocculated carbonnanotube film, or one pressed carbon nanotube film. When the carbonnanotube layer 12 comprises at least two carbon nanotube films, thecarbon nanotube layer 12 comprises at least two films of the drawncarbon nanotube film, the flocculated carbon nanotube film, and thepressed carbon nanotube film stacked with each other.

The drawn carbon nanotube film is directly drawn from a super-alignedcarbon nanotube array. Examples of a method of drawing the drawn carbonnanotube film is taught by US patent application US 20080248235 A1 toFeng et al.

FIG. 2 illustrates the drawn carbon nanotube film includes a number ofcarbon nanotubes that are arranged substantially parallel to a surfaceof the drawn carbon nanotube film. A large number of the carbonnanotubes in the drawn carbon nanotube film can be oriented along apreferred orientation, meaning that a large number of the carbonnanotubes in the drawn carbon nanotube film are arranged substantiallyalong the same direction. An end of one carbon nanotube is joined toanother end of an adjacent carbon nanotube arranged substantially alongthe same direction, by van der Waals force, to form a free-standingfilm. A minority of carbon nanotubes in the drawn carbon nanotube filmmay be randomly aligned. However, the number of randomly aligned carbonnanotubes is very small and does not affect the overall orientedalignment of the majority of carbon nanotubes in the drawn carbonnanotube film.

The majority of the carbon nanotubes in the drawn carbon nanotube filmsubstantially aligned along the same direction may not be exactlystraight, and can be curved to a certain degree, or are not exactlyaligned along the overall aligned direction, and can deviate from theoverall aligned direction by a certain degree. Therefore, partialcontacts can exist between the randomly aligned carbon nanotubes andadjacent carbon nanotubes.

The drawn carbon nanotube film includes a plurality of successivelyoriented carbon nanotube segments joined end-to-end by van der Waalsforce. Each carbon nanotube segment includes a plurality of carbonnanotubes substantially parallel to each other, combined together by vander Waals force. A plurality of microporous can be formed among theplurality of carbon nanotubes.

When the carbon nanotube layer 12 comprises at least two carbon nanotubefilms, an angle is formed between the carbon nanotubes of adjacent twocarbon nanotube drawn films. The angle ranges from 0° to 90°. The numberof the drawn carbon nanotube films of the carbon nanotube layer 12 isnot limited. In one embodiment, the carbon nanotube layer 12 comprisesten drawn carbon nanotube films stacked with each other, and the carbonnanotubes of adjacent drawn carbon nanotube films are Vertical crossedto form a plurality of micropores.

FIG. 3 and FIG. 4 illustrate a pressed carbon nanotube film which caninclude a number of carbon nanotubes isotropically arranged along a sameor different directions. Adjacent carbon nanotubes are attracted to eachother and combined by van der Waals force. A planar pressure head can beused to press the carbon nanotubes array along a direction perpendicularto a substrate; thereby a pressed carbon nanotube film having aplurality of isotropically arranged carbon nanotubes can be obtained. Aroller-shaped pressure head can be used to press the carbon nanotubesarray along a fixed direction, thereby a pressed carbon nanotube filmhaving a plurality of carbon nanotubes aligned along a fixed directionis obtained. The roller-shaped pressure head can also be used to pressthe array of carbon nanotubes along different directions, thereby apressed carbon nanotube film having a plurality of carbon nanotubesaligned along different directions is obtained. Examples of pressedcarbon nanotube films are taught by US PGPub. 20080299031A1 to Liu etal.

An area and a thickness of pressed carbon nanotube film can be selectedaccording to actual needs. The area of the pressed carbon nanotube filmis substantially the same as a size of the carbon nanotube array. Thethickness of the pressed carbon nanotube film is related to a height ofthe carbon nanotube array and a pressure of the rolling. The thicknessof the pressed carbon nanotube film can range from about 1 micrometer toabout 1 millimeter. The higher the height of the carbon nanotube arrayand the lower the pressure of the rolling, the larger the thickness ofthe pressed carbon nanotube film, on the contrary is also true. Gaps areformed between adjacent carbon nanotubes of the pressed carbon nanotubefilm, thus the pressed carbon nanotube film comprises a plurality ofmicropores. An aperture of each of the micropores is less than 10microns.

FIG. 5 illustrates the flocculated carbon nanotube film includes aplurality of carbon nanotubes entangled with each other to form anetwork structure. A length of each of the plurality of carbon nanotubesis larger than 10 micrometers. In one embodiment, the length of each ofthe plurality of carbon nanotubes is larger than or equal to 200micrometers and less than or equal to 900 micrometers. The carbonnanotubes can be substantially uniformly distributed in the flocculatedcarbon nanotube film. The flocculated carbon nanotube film comprises aplurality of micropores. An aperture of each of the micropores is lessthan 10 microns. The plurality of carbon nanotubes of the flocculatedcarbon nanotube film are entangled with each other, therefore, theflocculated carbon nanotube film has good flexibility and is afree-standing film. The free-standing film can be bent into any shapewithout breaking. An area and a thickness of the flocculated carbonnanotube film can be selected according to actual needs. The thicknessof the flocculated carbon nanotube film can range from about 1micrometer to about 1 millimeter. In one embodiment, the thickness ofthe flocculated carbon nanotube film is about micrometer. Theflocculated carbon nanotube film can be formed by flocculating thecarbon nanotube array. Examples of the flocculated carbon nanotube filmare taught by U.S. Pat. No. 8,808,589 to Wang et al.

Since the carbon nanotube layer 12 has a viscosity, the carbon nanotubelayer can be adhered to the inner surface of the blackbody radiationcavity 11 without using an adhesive. Of course, in order to ensure thatthe carbon nanotube layer is closely combined with the inner surface ofthe black body radiation cavity 11, the adhesive can be coated on theinner surface to make the carbon nanotube attached to the inner surfacefirmly.

The cavity blackbody radiation source in this disclosure has manyadvantages. First, carbon nanotubes are currently the darkest materialin the world, the emissivity of carbon nanotubes is 99.6%, which is farlarger than that of currently surface material of the inner wall of theblack body cavity. For example, an emissivity of the Nextel Velvet 81-21black lacquer is only 96%. Therefore, the emissivity of carbon nanotubecomposites comprising the carbon nanotubes and black lacquer is alsolarger than that of the surface material of currently inner wall of theblackbody cavity.

Second, currently, the cavity blackbody radiation source obtains alarger emissivity by using large emissivity coating material, increasinga depth of the blackbody radiation cavity and reducing the caliber.However, the cavity blackbody radiation source of this disclosure adoptsthe carbon nanotube composite material as the inner surface material ofthe blackbody radiation cavity, the depth of the blackbody radiationcavity is greatly reduced under the same effective emissivity of thecavity, and therefore, a miniaturization of the cavity blackbodyradiation source can be realized.

Third, the carbon nanotubes can be prepared by a chemical vapordeposition of carbon source gas under high temperature conditions, andthe raw materials are cheap and easy to obtain.

Fourth, the carbon nanotubes have excellent thermal conductivity, usingthe carbon nanotube layer as the inner surface material of the blackbody radiation cavity can improve the temperature uniformity andstability of the black body radiation source.

Fifth, the carbon nanotubes have excellent mechanical properties. Theuse of carbon nanotube materials to prepare cavity blackbody radiationsources can increase the stability of the cavity blackbody radiationsource, and make the star borne blackbody not easy to damage in harshenvironments.

FIG. 6 shows a method of making the cavity blackbody radiation source10, in one embodiment. The method comprises:

-   -   block (B11), providing the blackbody radiation cavity 11, the        blackbody radiation cavity 11 comprises an inner surface;

block (B12), providing a support and the carbon nanotube layer 12, andwrapping the carbon nanotube layer 12 on a surface of the support toform a carbon nanotube tubular structure;

-   -   block (B13), inserting the carbon nanotube tubular structure        into the black body radiation cavity 11, and making the carbon        nanotube tubular structure bonded to the inner surface; and    -   block (B14), removing the support.

In block (B11), the blackbody radiation cavity 11 is an integralcylindrical structure. A material of the blackbody radiation cavity 11is an aluminum alloy. The blackbody radiation cavity 11 comprises a room112. The cavity 113 is cylindrical. A bottom surface of the room 112 isa flat surface.

In one embodiment, block (B12) comprises: providing a film and fixingthe carbon nanotube layer on a surface of the film; and rolling the filminto a cylindrical structure, in which a side of the carbon nanotubelayer faces outward to form the carbon nanotube tubular structure. Thefilm has excellent flexibility, and the film can be a poly(ethyleneterephthalate) (PET) film, a polydimethylsiloxane (PDMS) film or thelike. A size of the carbon nanotube tubular structure can be adjustedaccording to a size of the black body radiation cavity 11. In oneembodiment, the film is the PET film. The carbon nanotube layer 12comprises ten drawn carbon nanotube films stacked with each other, andthe carbon nanotubes in adjacent drawn carbon nanotube films arevertically crossed to form a plurality of micropores.

In one embodiment, block (B12) comprises: providing a cylindricalsupport and wrapping the carbon nanotube layer on an outer surface ofthe support to form the carbon nanotube tubular structure. A material ofthe support is a polymer material. A diameter of the support is slightlysmaller than a diameter of the room 112.

In block (B13), in order to ensure that the carbon nanotube layer isclosely combined with the inner surface of the black body radiationcavity 11, an adhesive can be coated on the inner surface to make thecarbon nanotube layer attached to the inner surface firmly.

In one embodiment, the method further comprises wrapping the heatingelement on the outer surface of the blackbody radiation cavity 11, andthe blackbody radiation cavity 11 can be heated in real time.

FIG. 7 shows a cavity blackbody radiation source 20 of one embodiment. Astructure of the cavity black body radiation source 20 is substantiallythe same as that of the cavity black body radiation source 10. Thecavity black body radiation source 20 comprises a blackbody radiationcavity 21, a carbon nanotube layer 22, and a black lacquer 23. Theblackbody radiation cavity 21 comprises an inner surface. The blacklacquer 23 is located on the inner surface. The carbon nanotube layer 22is located on a surface of the black lacquer 23 away from the blackbodyradiation cavity 21. The carbon nanotube layer 22 is the same as thecarbon nanotube layer 12.

The blackbody radiation cavity 21 comprises a blackbody cavity 210 and ablackbody cavity bottom 211. The blackbody cavity 210 and the blackbodycavity bottom 211 can be an integral structure. The blackbody cavity 210has a room 212. The room 212 has a circular cross section.

The black lacquer 23 has high emissivity, such as Pyromark 1200 blacklacquer having an emissivity 0.92, Nextel Velvet 811-21 black lacquerhaving an emissivity 0.95. In one embodiment, the black lacquer 23 isthe Nextel Velvet 811-21 black lacquer. A thickness of the black lacquer23 can not be too small or too large. When the thickness of the blacklacquer 23 is too small, a binding force between the carbon nanotubelayer 22 and the inner surface of the blackbody radiation cavity 21 isweak, and the carbon nanotube layer 22 cannot be firmly fixed to theinner surface of the black body radiation cavity 21. On the contrary,when the thickness of the black lacquer 23 is too large, the carbonnanotube layer 22 is embedded in the black lacquer 23, therefore, astructure of the carbon nanotube layer 22 is destroyed, and a highemissivity of the carbon nanotube layer 22 cannot be exhibited.

FIG. 8 shows a method of making the cavity blackbody radiation source20, in one embodiment. The method comprises:

-   -   block (B21), providing the blackbody radiation cavity 21        comprising an inner surface, and coating the black lacquer 23 on        the inner surface;    -   block (B22), providing a support and the carbon nanotube layer        22, and wrapping the carbon nanotube layer 22 on a surface of        the support to form a carbon nanotube tubular structure;    -   block (B23), inserting the carbon nanotube tubular structure        into the black body radiation cavity 21, and attaching the        carbon nanotube tubular structure on the inner surface; and    -   block (B24), removing the support.

The method of making the cavity blackbody radiation source 20 is thesame as the method of making the cavity blackbody radiation source 10except block (B21). The black lacquer 23 has high emissivity, such asPyromark 1200 black lacquer having an emissivity 0.92, Nextel Velvet811-21 black lacquer having an emissivity 0.95. In one embodiment, theblack lacquer 23 is the Nextel Velvet 811-21 black lacquer.

The black lacquer 23 is located between the inner surface and the carbonnanotube layer 22, therefore, the carbon nanotube layer 22 can be morefirmly bonded to the inner surface of the black body radiation cavity21. Furthermore, the black lacquer is a high emissivity material, sothat the emissivity of the cavity blackbody radiation source 20 can befurther improved.

It is to be understood that the above-described embodiments are intendedto illustrate rather than limit the present disclosure. Variations maybe made to the embodiments without departing from the spirit of thepresent disclosure as claimed. Elements associated with any of the aboveembodiments are envisioned to be associated with any other embodiments.The above-described embodiments illustrate the scope of the presentdisclosure but do not restrict the scope of the present disclosure.

Depending on the embodiment, certain of the steps of a method describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may includesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A cavity black body radiation source comprising:a blackbody radiation cavity comprising an inner surface; a blacklacquer located on the inner surface; and a carbon nanotube layerlocated on a surface of the black lacquer away from the blackbodyradiation cavity, wherein the carbon nanotube layer comprises aplurality of carbon nanotubes and a plurality of microporous.
 2. Thecavity blackbody radiation source of claim 1, wherein the carbonnanotube layer comprises at least one carbon nanotube film.
 3. Thecavity blackbody radiation source of claim 2, wherein the at least onecarbon nanotube film is a drawn carbon nanotube film, a flocculatedcarbon nanotube film or a pressed carbon nanotube film.
 4. The cavityblackbody radiation source of claim 3, wherein the carbon nanotube layercomprises at least two carbon nanotube films stacked with each other,and the at least two carbon nanotube films comprises at least two filmsof the drawn carbon nanotube film, the flocculated carbon nanotube film,and the pressed carbon nanotube film.
 5. The cavity blackbody radiationsource of claim 3, wherein the drawn carbon nanotube film comprises aplurality of carbon nanotubes, and the plurality of carbon nanotubes arearranged substantially along a same direction.
 6. The cavity blackbodyradiation source of claim 3, wherein the pressed carbon nanotube filmcomprises a plurality of carbon nanotubes, and the plurality of carbonnanotubes are isotropically arranged along a same or differentdirections.
 7. The cavity blackbody radiation source of claim 3, whereinthe flocculated carbon nanotube film comprises a plurality of carbonnanotubes, and a network structure is formed by the plurality of carbonnanotubes entangled with each other by Van der Waals force.
 8. Thecavity blackbody radiation source of claim 1, wherein the carbonnanotube layer is adhered to the inner surface without using anadhesive.
 9. The cavity blackbody radiation source of claim 1, wherein amaterial of the blackbody radiation cavity is hard aluminum material,aluminum alloy material or oxygen-free copper.
 10. The cavity blackbodyradiation source of claim 1, wherein the blackbody radiation cavitycomprises an outer surface, and the cavity blackbody radiation sourcecomprises a heating element wrapped or wound around the outer surface ofthe blackbody radiation cavity.
 11. The cavity blackbody radiationsource of claim 9, wherein the heating element comprises a carbonnanotube structure, a first electrode and a second electrode, the firstelectrode and the second electrode are located on a surface of thecarbon nanotube structure and spaced apart from each other.
 12. Thecavity blackbody radiation source of claim 1, wherein the black lacqueris a Pyromark 1200 black lacquer or a Nextel Velvet 811-21 blacklacquer.
 13. A method of making the cavity blackbody radiation sourcecomprising: step (S11), providing a blackbody radiation cavitycomprising an inner surface and a black lacquer, a support and a carbonnanotube layer; and coating the black lacquer on the inner surface; step(S12), wrapping the carbon nanotube layer on a surface of the support toform a carbon nanotube tubular structure; step (S13), inserting thecarbon nanotube tubular structure into the black body radiation cavity,and attaching carbon nanotube tubular structure on the inner surface;and step (S14), removing the support.
 14. The method of claim 13,wherein the support is a film comprising a surface, step (S12)comprises: fixing the carbon nanotube layer on the surface of the film;and rolling the film into a cylindrical structure, and a side of thecarbon nanotube layer faces outward to form the carbon nanotube tubularstructure.
 15. The method of claim 14, wherein a material of the supportis a flexible material.
 16. The method of claim 14, wherein the supportcomprises an outer surface, and step (S12) comprises: providing acylindrical support and wrapping the carbon nanotube layer on the outersurface of the support to form the carbon nanotube tubular structure.17. The method of claim 13, wherein the blackbody radiation cavitycomprises an outer surface, and after step (S14), further compriseswrapping a heating element on the outer surface of the blackbodyradiation cavity.
 18. The method of claim 17, wherein the heatingelement comprises a carbon nanotube structure, a first electrode and asecond electrode, the first electrode and the second electrode arelocated on a surface of the carbon nanotube structure and spaced apartfrom each other.